Pasteur as a student examined in detail the supposed isomorphism of the (+) tartrate and the inactive racemate salts. At ambient temperature the inactive sodium ammonium racemate gave hemihedral crystals of two enantiomorphous types, separable by hand sorting, one type having the morphology of the corresponding (+)-tartrate crystals and the other exhibiting mirror-image facets. In solution each crystal type was optically active, the specific rotations having an equal magnitude but opposed signs. The conclusion of Pasteur, that the molecular structures of (+)- and (−)-tartaric acid have mirror-image morphologies, like the corresponding crystal forms, was taken up only 25 years later, notably by Le Bel. Meanwhile, on repeating the work of Pasteur in Italy, at a temperature above the transition point (27degree C.), Scacchi (1865) obtained only one crystal type, with a holohedral form, that of sodium ammonium racemate with both (+)- and (−)-tartrate in a single centrosymmetric lattice.
Before the time of Pasteur, enantiomeric substances were termed ‘physical isomers’, since they appeared to differ in no respect other than the property of rotating the plane of polarized light in a clockwise or anticlockwise sense. Pasteur added to this property three types of chemical or physical chiral recognition and discrimination, summed up in his review lectures on molecular dissymmetry of 1860. Pasteur coined the term ‘dissymmetric’ to describe structural forms, which are not superposable by translations and rotations alone upon the corresponding mirror-image structure. The equivalent term ‘chiral’ (handed) was introduced by Kelvin in his Baltimore lectures of 1884 (Kelvin, 1904). The first type of chiral discrimination identified by Pasteur is the preferential co-crystallization of an enantiomer with its optical antipode, shown by the majority of racemates, which crystallize as such from solution or from the melt. Only some 250 cases have been identified, of the many-thousand studied, where a racemate forms a conglomerate of two enantiomorphous crystal types, each type containing a single optical isomer. These are the relatively rare cases of ‘spontaneous resolution by crystallization’. The second of Pasteur's discoveries, diastereomeric discrimination, covers the different chemical and physical properties of salts and other combinations of the two optical isomers in a racemate with a single enantiomer of another chiral substance (+)-A(+)-B and (−) A(+)-B. The unequal solubilities of such diastereomers afford a general procedure for the optical resolution of racemates. The third discrimination, reflecting Pasteur's growing preoccupation with microbiology, appeared in the biochemical selectivity of micro-organisms between the two enantiomers in a racemic mixture, exemplified by the metabolism of specifically the (+)-isomer of racemic tartaric acid by Penicillium moulds.
Diastereomeric discrimination is commonly used to prepare single enantiomers by first reacting the racemate with a diastereomeric catalyst/reactants so as to obtain diastereomeric compounds. These diastereomeric compounds are then separated by making use of their different solubilities in different solvents, or by other physical or chemical techniques.
In some cases microbes are used to separate enantiomers from racemates, where a biochemical reaction is possible.
In this invention we are mostly interested in the first type of separation, where physical methods or physical properties are employed. Due to the two enantiomers being very similar in physical and chemical properties, this has been the very difficult task. Other physical methods include use of circularly polarized light to enrich the preferred handedness of the enantiomers. Differential absorption of the circularly polarized light between the right handed molecule and left handed molecule is also proposed to separate the enantiomers from the racemate by utilizing the momentum transfer of the light in absorbing molecules in overcoming the diffusion process.
Mason describes optical activity in molecular spectroscopy in the reference. In Cotton effect, by using plane-polarized light, Cotton was able to show that there is a reversal of sign of the optical rotation at one wave length (lambda. max) on scanning through an absorption band with respect to wavelength, and found the emerging radiation to be elliptically polarized, on account of the differential absorption of the left circularly polarized LCP and the right circularly polarized RCP components of the incident radiation. For positive Circular Dichroism (CD) absorption, measured as a differential extinction coefficient between left and right circularly polarized light, the optical rotation changes sign from positive at long wavelength to negative at shorter wavelength; with the converse sign change if the CD absorption is negative. One can therefore differentiate between a right-handed and a left-handed sample by measuring the Optical Rotatory Dispersion (ORD) or CD. Measuring systems such as spectrophotometers for CD and circular intensity differential (CID) in the luminescence of the excited molecules are described in the reference by Mason.
Microfluidic systems are fairly new micro-devices and are described in the patents U.S. Pat. Nos. 6,123,316 and 5,962,081 and the references therein. Conduit systems are a critical part of many micron and millimeter scale micro-devices which are widely used in valve-containing microfluidic controls systems, micro-sensors, and micro-machines. Currently, micro-device valves are used in automobiles, medical instrumentation, or process control applications, and in conjunction with appropriate sensors can provide accurate determinations of pressure, temperature, acceleration, gas concentration, and many other physical or chemical states. Microfluidic controls include micro-valves for handling gases or liquids, flow gauges, and ink jet nozzles, while micro-machines include micro-actuators, movable micro-mirror systems, or even tactile moving assemblies. In part because of the ease of associating and integrating electronic control circuitry (using VLSI techniques), micro-devices are commonly constructed from glasses or semiconductor material substrates such as crystalline silicon, commercially available in the form of semiconductor wafers used for production of integrated circuits. Lately, the substrates have been fabricated with molded plastic materials and are described in the Nanostream, Inc. brochures and literature. Microfluidic systems make it possible to make and transport samples with pico-liter quantities.
Many commercial inkjet printers started to appear about a decade ago. At the present time the resolution of these printers are so good that United States Treasury has been redesigning its paper currency so that the printers will not be able to reproduce them so that they can use the counterfeits as passable currency. The commercial printers are manufactured by Hewlett-Packard, Lexmark, Hitachi and Xerox and were adapted from the thermal bubble technology developed by Canon and adding enhancements along the way in their patents. Epson on the other hand use piezoelectric crystals to do the job of the bubbles in inkjet printers. In Epson's line of printers, microscopic piezoelements subjected to tiny charges are distorted, pushing out tiny droplets of ink. Modest injet printers have a resolution of about 300 dots per inch. High-resolution printers made by Hewlett Packard and Hitachi are 1200 dots/inch. Also about 5000 or more droplets can be squirted in a second in a precise manner. Scientists at MIT and Sandia National laboratories have been able to put molecules into a solution and squirted out onto various surfaces with an inkjet printer to form pattern designed by a computer and in very small quantities. Very recently also, scientists at University of North Carolina have been able to design software to be able to make inkjets that has smaller droplet sizes from the same injectors.
Hammer and Inoue, et. al, have described spectrophotometers recently in the two patents U.S. Pat. Nos. 6,002,477 and 4,169.678. respectively. A commercial model is also described in the Varian Cary spectophotometers by Varian, where phosphorescence data can be captured every microsecond where sensitivity of pico-molar concentrations are measured with ease.
Purdie in U.S. Pat. No. 5,593,894 described an invention relating to the direct quantitative determination of cholesterol and involves the formation of a spectrophotometrically active product of cholesterol obtained by contacting cholesterol with an acyl compound and a perchlorate effective to form the spectrophotometrically active product.
Futekov et. al, in U.S. Pat. No. 4,494,871 described a dosing device for emitting liquid samples to an automatic absorption spectrophotometer having a liquid atomizer for the samples, utilizes at least one three-way distributor, one of the ports of which communicates with the atomizer, another port of which communicates with the spectrophotometer, and a third part of which communicates with a vessel containing the liquid sample. An electromagnetic valve is provided for the port communicating with the atmosphere. In the preferred embodiment, two such distributors are provided in series and the second distributor is connected to a source of pure solvent and is interposed between the first distributor and the spectrophotometer.
Biegelsen, et. al, in U.S. Pat. No. 6,123,316 described conduit system for a valve array whereby the fluid conduit systems is constructed in printed circuit boards or other dielectric laminate substrates. The fluid conduits can be angled or curved to provide greater directional control of fluid flow. Conduits are created by lamination of a first laminate layer and a second laminate layer. The first laminate layer is composed of a dielectric base material impregnated with a resin, with a first aperture defined therethrough, while the second laminate layer has a second aperture. The second aperture is positioned with respect to the first aperture to only partially overlap, together defining an angled conduit. Fluid flow through the conduits can be controlled using microdevice valves.
Ohman et. al, in U.S. Pat. No. 5,962,081 described a method for the manufacture of a microstructure having a top face and a bottom face, at least one hole or cavity therein extending from the top face to the bottom face, and a polymer membrane which extends over a bottom opening of said hole or cavity, which method comprises the steps of: providing a substrate body having said top and bottom faces, optionally forming at least part of said at least one hole or cavity in the substrate body, providing a membrane support at the bottom face opening of said at least one hole or cavity, depositing a layer of polymer material onto the bottom face of said substrate body against said membrane support, if required, completing the formation of the at least one hole or cavity, and, if not done in this step, selectively removing said membrane support to bare said polymer membrane over the bottom opening of the at least one hole or cavity.
Yeng, et. al, in U.S. Pat. No. 5,504,221 described a method for resolving racemic dimethyl-4,4′-dimethoxy-5,6,5′,6′-di(methylenedioxy)biphenyl-2,2′-dicarbox ylate (“DDB”), in which a chiral .alpha.-alkyl benzyl alcohol is used as the resolving agent. More specifically, racemic DDB is first hydrolyzed to form dicarboxylic acid, which is then reacted with chiral .alpha.-alkyl benzyl alcohol to form two chiral isomers. The chiral isomers, after separation either by chromatography or by recrystallization, are respectively hydrogenated and esterified to form chiral DDB isomers.
Zepp, et al, in U.S. Pat. No. 5,196,568 described an invention relating to novel compositions of matter, which are esters with enhanced water solubility, for use in aqueous enzymatic resolution reactions of racemic mixtures of these esters for producing the separate chiral isomers of the racemic mixture. The invention also relates to novel methods for preparing these esters. The importance of the production of the separate chiral isomers of the racemic mixtures resides in the isolation of the isomers that frequently have different biological activities. Of particular significance regarding the water-soluble esters of this invention is that they are derivatized with groups, which enhance their aqueous solubility and their reactivity with enzymatic resolving methods, which are mediated in an aqueous environment. In addition, the importance of these compounds resides in their being useful in novel methods for facilitating the enzymatic resolution reactions of racemic mixtures of esters, which are derivatized with groups which enhance the esters' aqueous solubility, in 1) a homogeneous aqueous reaction system where an extractive phase is not present, 2) a multiphase dispersion extractive reaction where an extractive phase is present, and 3) an extractive membrane reactor where the enzyme is placed alternatively either (a) in the aqueous phase, (b) in association with the membrane, or (c) in the aqueous phase and in association with the membrane, wherein the aqueous ester phase is contacted with one side of the membrane, and where an organic extractive phase is contacted with the other side of the membrane, wherein the extractive phase serves to remove the resolving reaction product.
Matson, et al. in U.S. Pat. No. 5,077,217 described a method for membrane reactor resolution of stereoisomers.
This invention relates to novel methods for facilitating the enzymatic resolution of racemic mixtures of esters, which are derivatized with groups which enhance the esters' aqueous solubility, in an extractive member reactor where the enzyme is placed alternatively either (1) in the aqueous phase, (2) in association with the membrane, or (3) in the aqueous phase and in association with the membrane, wherein the aqueous ester phase is contacted with one side of the membrane, and where an organic extractive phase is contacted with the other side of the membrane, wherein the extractive phase serves to remove the resolving reaction product. Of particular significance regarding this invention is its use of water-soluble esters that are derivatized with groups, which enhance their aqueous solubility and their reactivity with enzymatic resolving methods, which are mediated in an aqueous environment. Novel methods were utilized to prepare these esters, for use in this invention's methods for enzymatically resolving the racemic mixtures of the esters, to produce the separate chiral isomers of the racemic mixture. The importance of the resolution of the separate chiral isomers of the racemic mixtures resides in the isolation of the isomers that frequently have different biological activities.
Mills, W. H., in Chem. Ind., 1932, 5, 750–59, used statistical model to explain how a racemate is formed from an achiral starting material where the formation of a small excess of one of the enanatiomers has a significant probability.
Rhinehart, E. A., et al, in UC LLL Report—UCRL51833, Apr. 14, 1975 described Bulk Atomic or Molecular Separations by Resonant Radiation Pressure.
Lethokov, V. S., in Opt. Comm. 1973, 7, 1, 59–60 described an optical separation of isomeric nuclei by laser radiation.
Shuming N., et al, in Anal. Chem. 1995, 67,2849–2857 described the real-time detection of single molecules in solution by confocal fluorescence microscopy, indicating how small sample quantities of chemicals can be detected by optical means.
Chung-yi, K., et al, in Appl. Opt., 1999, 38,9 1481–1487 described instrumentation for real-time detection of single-molecule fluorescence in guided streams of 1-micro-meter water droplets. Target molecules were confined to droplets whose volumes were comparable with illumination volumes in diffraction-limited fluorescence microscopy and guided to the waist of cw probe laser.
Chen A. U., et al, Phys. Fluids, 2002, 14, 1, L1–L4 showed a new method for significantly reducing drop radius without reducing nozzle radius in drop-on-demand drop production. Computational and experimental analysis of dynamics of drop formation is also given by one of the authors (Barasan) in previous publications mentioned in the references.